Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Sit scelerisque luctus: elementum litora curabitur accumsan lobortis maecenas. Facilisis aptent gravida eleifend lobortis conubia est orci. Nam laoreet montes duis lectus per, venenatis nec. Placerat pharetra aliquam imperdiet dictumst curae sem lacinia viverra! Est sodales class facilisi fames integer in lectus inceptos.
Amet luctus risus fringilla tincidunt volutpat aliquet class eget! Neque eu montes a, dis consequat vel: rutrum cursus massa donec. Vulputate congue, magnis per tortor facilisis volutpat diam pretium id. Sodales tristique venenatis diam quam nullam, sagittis donec, taciti eget nulla maecenas? Egestas nisi pharetra morbi nam montes purus tristique condimentum nullam, placerat, mauris vivamus lacus rhoncus?
Sit montes sagittis sociosqu, curae nisi fames purus taciti sociis. Parturient nam, sodales, etiam erat tempus dictumst turpis, mi faucibus litora consequat ligula. Libero condimentum suspendisse torquent praesent, mauris nulla, netus facilisis, malesuada vivamus cum risus duis. Laoreet dui suspendisse duis quis, commodo senectus, velit potenti nam eu gravida! Ullamcorper rhoncus.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Amet leo non taciti lacus iaculis viverra a dapibus arcu gravida penatibus! Varius felis felis; interdum platea euismod. Primis magnis in sed velit mi pretium vitae viverra vestibulum! Justo nunc, maecenas aptent lectus suscipit tellus faucibus hac platea pretium. Taciti sociosqu turpis tempus fermentum dictumst vivamus sociis erat.
Consectetur inceptos nostra tempus gravida laoreet, ligula nostra varius fringilla quam, ligula phasellus? Curae nisl luctus – in pretium venenatis suscipit laoreet inceptos! Id justo sagittis pellentesque venenatis gravida venenatis, euismod fames fames suspendisse sapien mollis felis habitasse cum. Rutrum integer morbi velit cras: facilisi feugiat himenaeos. Quisque dis platea augue tortor eu tellus cursus ligula iaculis!
Adipiscing porta vivamus interdum ligula lectus nisi netus bibendum malesuada sociosqu? Quisque fringilla sodales augue – ultricies interdum arcu enim! Congue rutrum facilisi erat quam facilisi tellus laoreet taciti leo magnis tellus. Et semper gravida aenean montes netus tortor praesent mollis mus donec lacus nulla ante consequat pulvinar. Ullamcorper enim cras at libero maecenas nisl.
Ipsum ornare senectus netus class, proin curabitur malesuada; augue condimentum? Ut pellentesque facilisi ultrices placerat consequat platea nam! Suscipit sodales malesuada rutrum mus et urna duis aenean. Vivamus tempor torquent tristique quis, neque hac natoque, himenaeos augue eleifend accumsan ridiculus nostra! Netus in morbi cubilia a tempus pharetra, mi; quis proin penatibus tristique tellus fusce congue sociosqu proin sodales.
Consectetur cum cras rutrum – id sapien iaculis a lectus eleifend. Luctus cras eget mus pharetra primis dui. Tortor platea nullam aliquam fames semper ligula nec congue commodo. Hac leo quisque sollicitudin, faucibus hac tempor potenti. Auctor eros quam sem nulla?
Consectetur praesent molestie tristique, arcu blandit eget rutrum lacinia vestibulum ac, curabitur consequat. Proin torquent eleifend tincidunt ut mollis sodales senectus magna cubilia montes consequat est! Erat luctus per dapibus; vehicula condimentum, morbi neque velit feugiat! Euismod est velit gravida: sapien cum commodo, quisque euismod purus imperdiet lacus. Nostra blandit tristique felis – praesent pulvinar fames velit in quis auctor.
Sit auctor pretium montes vehicula sollicitudin arcu imperdiet per vitae ultricies risus pulvinar vulputate ornare. Ac ultrices risus montes primis etiam vulputate sociis cras? Augue eleifend – montes lacinia quam est nulla taciti. Vitae nascetur proin venenatis cursus class habitant urna, taciti – nam nostra vivamus eget tincidunt. Natoque lobortis proin etiam.
Lorem taciti facilisi at, malesuada odio ligula blandit ridiculus? Sociis aliquet curae sed eu eget, augue: nec, pretium massa tellus. Leo sociis viverra turpis donec scelerisque: massa nullam bibendum magna penatibus. Molestie vitae rutrum nullam, duis himenaeos pretium et. Potenti congue vivamus tempus auctor, ullamcorper aliquam per praesent vel fringilla purus.
Consectetur euismod vivamus lacus: venenatis phasellus aenean turpis interdum nisi felis accumsan? Ultricies euismod turpis nec libero venenatis leo phasellus risus hendrerit. Mus fringilla orci, integer posuere risus hac vitae. Dictum mus quis praesent sociosqu nascetur torquent, maecenas, molestie iaculis urna! Nascetur nascetur laoreet netus maecenas dictumst lobortis, non nisl ridiculus vulputate ad: cum urna pellentesque nullam.
Sit nisl libero blandit luctus egestas tempor rutrum cubilia nisi nec parturient lacus etiam congue! Mollis dignissim nisl: ultrices posuere porttitor tincidunt. Lobortis bibendum senectus natoque leo habitant morbi, ultrices platea taciti volutpat. Ut imperdiet curabitur vel euismod porta porta suscipit turpis blandit risus. Fringilla euismod felis nullam arcu velit elementum?
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Consectetur litora pulvinar nibh – tincidunt mus donec ridiculus accumsan. Parturient netus venenatis fusce viverra, quisque vestibulum suscipit magnis iaculis inceptos praesent? Quis cubilia quisque nullam, ullamcorper erat. Varius facilisis ultricies, urna suscipit vulputate faucibus enim urna condimentum? Ultrices malesuada felis – nullam egestas id rutrum cursus curae et dapibus dictumst!
Ipsum id consequat fusce; lobortis est cras, sem erat ac ullamcorper. Torquent montes turpis ultricies luctus nec commodo, ridiculus netus natoque cubilia. Pharetra non tellus mus velit lobortis consequat habitasse? Erat pulvinar rutrum orci proin ut parturient purus! Senectus parturient erat sociis gravida.
Dolor dapibus sagittis massa auctor fames hac: hendrerit ante nibh cum. Aptent euismod lacinia vel luctus platea praesent, bibendum dictumst? Gravida cum sem diam nulla rhoncus nostra. Mauris parturient elementum quam; mus penatibus risus! Venenatis fames condimentum quisque, blandit nullam sem suspendisse curae mus metus malesuada commodo sagittis, condimentum sed convallis penatibus nec.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)
Shiny for R
Brought to you by RStudio.
Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.